Hi Jerry!
I generally understood how DDS works, but I'm bemused why the output frequencies do not correspond to the input frequencies?
1.) Yesterday I made a test with the GIVEN Soft Front Panel and even this does not work as it should: If I want a standard square function of 1 MHz, I get a square function of 2,5 Hz! (The same with 100 kHz = 0,25 Hz and 10 kHz = 0,025 Hz.) Where does this factor come from?
2.) This factor also corresponds more or less to the generated arbitrary function in my program: with 1 MHz I get 1,6 Hz, with 100 kHz = 0,16 Hz ...
3.) I thought changing the ratio between pulse length and length of the whole signal period (it's first a square and then a long time zero) I could generate a short pulse anyway accepting the mentioned f
requency discrepancies. E.g.: One period takes 600 ms (although my input frequency is 1 MHz). If I have a ration of 1 (square) to 100 (whole signal) I should get at least a pulse of 6 ms. But the shortest pulse I ever got was about 20 ms.
The IMPORTANT QUESTION: is there a physical limit for generating pulses (e.g. due to the inertia of the DDS method)?
I hope I could explain my problem more precisely. Thank you anyway!
Steffi